The invention pertains to control systems and, more particularly, to methods and apparatus for networking, configuring and operating field devices, controllers, consoles and other control devices.
The terms xe2x80x9ccontrolxe2x80x9d and xe2x80x9ccontrol systemsxe2x80x9d refer to the control of a device or system by monitoring one or more of its characteristics. This is used to insure that output, processing, quality and/or efficiency remain within desired parameters over the course of time. In many control systems, digital data processing or other automated apparatus monitor a device, process or system and automatically adjust its operational parameters. In other control systems, such apparatus monitor the device, process or system and display alarms or other indicia of its characteristics, leaving responsibility for adjustment to the operator.
Control is used in a number of fields. Process control, for example, is employed in the manufacturing sector for process, repetitive and discrete manufactures, though, it also has wide application in utility and other service industries. Environmental control finds application in residential, commercial, institutional and industrial settings, where temperature and other environmental factors must be properly maintained. Control is also used in articles of manufacture, from toasters to aircraft, to monitor and control device operation.
Modern day control systems typically include a combination of field devices, controllers, workstations and other more powerful digital data processing apparatus, the functions of which may overlap or be combined. Field devices include temperature, flow and other sensors that measure characteristics of the subject device, process or system. They also include valves and other actuators that mechanically, electrically, magnetically, or otherwise effect the desired control.
Controllers generate settings for the actuator-type field devices based on measurements from sensor type field devices. Controller operation is typically based on a xe2x80x9ccontrol algorithmxe2x80x9d that maintains a controlled system at a desired level, or drives it to that level, by minimizing differences between the values measured by the sensors and, for example, a setpoint defined by the operator.
Workstations, control stations and the like are typically used to configure and monitor the process as a whole. They are often also used to execute higher-levels of process control, e.g., coordinating groups of controllers and responding to alarm conditions occurring within them.
In a food processing plant, for example, a workstation coordinates controllers that actuate conveyors, valves, and the like, to transport soup stock and other ingredients to a processing vessel. The workstation also configures and monitors the controllers that maintain the contents of that vessel at a simmer or low boil. The latter operate, for example, by comparing measurements of vapor pressure in the processing vessel with a desired setpoint. If the vessel pressure is too low, the control algorithm may call for incrementally opening the heating gas valves, thereby, driving the pressure and boiling activity upwards. As the pressure approaches the desired setpoint, the algorithm requires incrementally leveling the valves to maintain the roil of the boil.
The field devices, controllers, workstations and other components that make up a process control system typically communicate over heterogeneous media. Field devices connect with controllers, for example, over dedicated xe2x80x9cfieldbusesxe2x80x9d operating under proprietary or industry-specific protocols. Examples of these are FoxCom(TM), Profibus, ControlNet, ModBus, DeviceNet, among others. The controllers themselves may be connected to one another, as well as to workstations, via backplane or other proprietary high-speed dedicated buses, such as Nodebus(TM). Communications among workstations and plant or enterprise-level processors may be via Ethernet networks or other Internet Protocol (IP) networks.
Control device manufacturers, individually, and the control industry, as a whole, have pushed for some uniformity among otherwise competing communication standards. The Foundation Fieldbus, for example, is the result of an industry-wide effort to define a uniform protocol for communications among processor-equipped (or xe2x80x9cintelligentxe2x80x9d) field devices. Efforts such as this have been limited to specific segments of the control hierarchy (e.g., bus communications among field devices) and are typically hampered by technological changes that all to soon render the standards obsolete.
Still less uniform are the command and operation of control devices. Though field devices may function at the direction of controllers and controllers, in turn, at the direction of workstations (or other plant-level processors), proprietary mechanisms within the individual components determine how they perform their respective functions. Even the commands for invoking those functions may be manufacturer- or product-specific. Thus, the commands necessary to drive actuators of one manufacturer will differ from those of another. How the corresponding commands are processed internally within the actuators differ still more (though, hopefully, the results achieved are the same). The specific programming codes used to effect a given control algorithm likewise differs among competing makes, as do those of the higher-level control processors.
Industry efforts toward harmonization of software for command and operation of control devices have focused on editing languages that define process control algorithms. This is distinct from the codes used to effect those algorithms within control devices and, rather, concerns software xe2x80x9ctoolsxe2x80x9d available to users to specify the algorithms, e.g., editors including IEC-1131 standard languages such as Field Blocks, Sequential Function Charts (SFC), Ladder Logic and Structured Text.
Less concerted are industry moves to extend monitoring and limited configuration capabilities beyond in-plant consoles, e.g., to remote workstations. An example of this was the abortive Java for Distributed Control (JDC) effort, which proposed enabling in-plant workstations to serve web pages to remote Java bytecode-enabled client computers. The latter used the to web pages to monitor and set control parameters which the workstations, in turn, incorporated into their own control schemes.
An academic system along these same lines was suggested by the Mercury Project of the University of Southern California, proposing the use of a web browser to enable remote users to control a robotic arm via a server that controlled the arm. A related company-specific effort included that announced by Tribe Computer Works that allegedly enabled users to manage routers and remote access servers over IP networks using web browser software. See, xe2x80x9cTribe Defines Net Management Role For Web Browser Software,xe2x80x9d Network World, May 22, 1995, at p. 14.
Thus sets the stage for the present invention, an object of which is to provide improved methods and apparatus for networking, configuring and operating field devices, controllers, consoles and other control devices. A related object is to provide such methods and apparatus for process control.
Further objects of the invention are to provide such methods and apparatus as reduce the confusion, complexity and costs attendant to prior art control systems.
Related objects of the invention are to provide such methods and apparatus as can be implemented with commercial off the shelf hardware and software.
Still further objects of the invention are to provide such methods and apparatus as achieve confusion-, complexity- and cost-reduction without hampering manufacturer creativity and without removing incentives to development of product differentiators.
The foregoing are among the objects attained by invention which provides, in one aspect, an improved field device for a process or other control system. The field device includes a virtual machine environment for executing Java byte code (or other such intermediate code) that, for example, configures the device to execute a control algorithm.
By way of non-limiting example, the field device can be an xe2x80x9cintelligentxe2x80x9d transmitter or actuator that includes a low power processor, along with a random access memory, a read-only memory, FlashRAM, and a sensor interface. The processor can execute a real-time operating system, as well as a Java virtual machine (JVM). Java byte code executes in the JVM to configure the field device to perform typical process control functions, e.g., for proportional integral derivative (PID) control and signal conditioning.
Further aspects of the invention provide a field device, such as a low-power intelligent actuator, that incorporates an embedded web server. This can be used to configure, monitor and/or maintain the device itself (as well as other elements of the control system) via a browser attached directly to the device or coupled to it over the network. To this end, the field device can incorporate a configuration editor, e.g., operating on a processor within the field device, that an end-user executes via the browser and web server.
Such a configuration editor can, in related aspects of the invention, be enabled or disabled depending on the environment in which it is used and more specifically, for example, the type of network in which it is incorporated. Thus, for example, the editor can be disabled when the field device is incorporated in a process control network that includes, e.g., an applications development environment suitable for configuration of the field device. Conversely, it can be enabled when the field device is incorporated in a network that lacks such a capability.
Still further aspects of the invention provide a field device as described above that includes an interface to an IP network, through which the device communicates with other elements of the control system. The IP network can be, for example, an Ethernet network. Moreover, it can be xe2x80x9cpowered,xe2x80x9d carrying electrical power as well as packets, datagrams, and other control or data signals. The field device, in related aspects of the invention, draws operational power, e.g., for its processor and other components, from such a network.
Yet further aspects of the invention provide a field device as described above that obtains configuration information and/or its network address from such an IP network upon start-up. To this end, on power-up or coupling to the network, the field device can supply an identifier (e.g., attained from a letterbug, assigned by a hub, or otherwise) to a DHCP or other server on the network. Once provided with an IP address, the field device can formally enter into the control network, e.g., by posting its characteristics to a network bulletin board, e.g., using a network enabler such as a Jini and/or JavaSpace server, or the like. Other network devices monitoring or notified via such a bulletin board can send configuration information to the field device or otherwise.
Still further aspects of the invention provide control devices, such as servers, control stations, operator consoles, personal computers, handheld computers, and the like, having attributes as described above. Such control devices can have other attributes, according to further aspects of the invention. Thus, by way of non-limiting example, they can provide web servers that collect process data from one or more control devices, generate source for operator displays, provide access to the control system, and host an applications development environment.
Still other aspects of the invention provide process, environmental, industrial and other control systems that comprise field and control devices as described above that are coupled via an IP network and, particularly, for example, by a powered IP network.
Additional aspects of the invention are directed to DHCP servers and network enablers (optionally, including web servers) for use in control systems as described above. Related aspects provide such servers and enablers as are embodied in solid state technologies, e.g., with no moving parts.
These and other aspects of the invention are evident in the attached drawings, and in the description and claims that follow.